Numerical study on the effect of steel fibers on fracture and size effect in concrete beams

The construction sector uses concrete extensively all around the world. Concrete contains a lot of microcracks even before it is loaded. When a tensile force is applied, these microcracks attempt to open up. While designing, the strength of concrete in its tensile zone is ignored. The strength and ductility of the concrete can be improved due to the addition of steel fibers. Steel fibers use a bridge mechanism to restrict the micro-cracks spread. This study uses ABAQUS to numerically analyze the behaviour of the Steel Fiber Reinforced Concrete (SFRC) beams. Two grades of concrete are studied, M20 and M60, for varying volumetric percentages of steel fibers. It was observed from the study that the ultimate load increases by around 52% and 41% for M25 and M60 grade concrete, respectively, by adding 1% of steel fiber. Fracture properties such as fracture toughness and fracture energy are calculated. The addition of steel fibers enhanced fracture toughness and energy significantly. Adding 1% fiber increases fracture toughness by around 56% and 34% and fracture energy by around 169% and 136% for M25 and M60 concrete, respectively. The size effect on SFRC beams is studied to determine the size-independent fracture parameters.